東華大學圖書館 |

Distribution and Sources of Black Carbon in the Arctic.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Distribution and Sources of Black Carbon in the Arctic./
作者:	Qi, Ling.
出版者:	Ann Arbor : ProQuest Dissertations & Theses, : 2016,
面頁冊數:	164 p.
附註:	Source: Dissertation Abstracts International, Volume: 78-06(E), Section: B.
Contained By:	Dissertation Abstracts International78-06B(E).
標題:	Atmospheric sciences. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=10246870
ISBN:	9781369413830

Distribution and Sources of Black Carbon in the Arctic.
Qi, Ling.

Distribution and Sources of Black Carbon in the Arctic. - Ann Arbor : ProQuest Dissertations & Theses, 2016 - 164 p.

Source: Dissertation Abstracts International, Volume: 78-06(E), Section: B.

Thesis (Ph.D.)--University of California, Los Angeles, 2016.

The Arctic is warming at twice the global rate over recent decades. To slow down this warming trend, there is growing interest in reducing the impact from short-lived climate forcers, such as black carbon (BC), because the benefits of mitigation are seen more quickly relative to CO2 reduction. To propose efficient mitigation policies, it is imperative to improve our understanding of BC distribution in the Arctic and to identify the sources. In this dissertation, we investigate the sensitivity of BC in the Arctic, including BC concentrations in snow (BCsnow) and BC concentrations in air (BCair), to emissions, dry deposition and wet scavenging using a global 3-D chemical transport model (CTM) GEOS-Chem. By including flaring emissions, estimating dry deposition velocity using resistance-in-series method, and including Wegener-Bergeron-Findeisen (WBF) in wet scavenging, simulated BCsnow in the eight Arctic sub-regions agree with the observations within a factor of two, and simulated BCair fall within the uncertainty range of observations. Specifically, we find that natural gas flaring emissions in Western Extreme North of Russia (WENR) strongly enhance BCsnow (by up to ?50%) and BCair (by 20--32%) during snow season in the so-called 'Arctic front', but has negligible impact on BC in the free troposphere. The updated dry deposition velocity over snow and ice is much larger than those used in most of global CTMs and agrees better with observation. The resulting BCsnow changes marginally because of the offsetting of higher dry and lower wet deposition fluxes. In contrast, surface BCair decreases strongly due to the faster dry deposition (by 27--68%). WBF occurs when the environmental vapor pressure is in between the saturation vapor pressure of ice crystals and water drops in mixed-phase clouds. As a result, water drops evaporate and releases BC particles in them back into the interstitial air. In most CTMs, WBF is either missing or represented by a uniform and low BC scavenging efficiency. In this dissertation, we relate WBF with temperature and ice mass fraction based on long-term observations in mixed-phase clouds. We find that WBF reduces BC scavenging efficiency globally, with larger decrease at higher latitude and altitude (from 8% in the tropics to 76% in the Arctic). WBF slows down and reduces wet deposition of BC and leave more BC in the atmosphere. Higher BC air results in larger dry deposition. The resulting total deposition is lower in mid-latitudes (by 12--34%) and higher in the Arctic (2--29%). Globally, including WBF significantly reduces the discrepancy of BCsnow (by ~50%), BCair (by ~50%), and washout ratios (by a factor of two to four). The remaining discrepancies in these variables suggest that in-cloud removal is likely still excessive over land. In the last part, we identify sources of surface atmospheric BC in the Arctic in springtime, when radiative forcing is the largest due to the high insolation and surface albedo. We find a large contribution from Asian anthropogenic sources (40--43%) and open biomass burning emissions from forest fires in South Siberia (29--41%). Outside the Arctic front, BC is strongly enhanced by episodic, direct transport events from Asia and Siberia after ~12 days of transport. In contrast, in the Arctic front, a large fraction of the Asian contribution is in the form of 'chronic' pollution on 1--2 month timescale. As such, it is likely that previous studies using 5- or 10-day trajectory analyses strongly underestimated the contribution from Asia to surface BC in the Arctic. Our results point toward an urgent need for better characterization of flaring emissions of BC (e.g. the emission factors, temporal and spatial distribution), extensive measurements of both the dry deposition of BC over snow and ice, and the scavenging efficiency of BC in mixed-phase clouds, particularly over Ocean. More measurements of 14C are needed to better understand sources of BC (fossil fuel combustion versus biomass burning) and to provide additional constrain on BC simulations.

ISBN: 9781369413830Subjects--Topical Terms:

3168354
Atmospheric sciences.

Distribution and Sources of Black Carbon in the Arctic.
LDR:04993nmm a2200301 4500 001 2118919
005 20170614101412.5
008 180830s2016 ||||||||||||||||| ||eng d
020 $a 9781369413830
035 $a (MiAaPQ)AAI10246870
035 $a AAI10246870
040 $a MiAaPQ $c MiAaPQ
100 1 $a Qi, Ling. $3 3280764
245 1 0 $a Distribution and Sources of Black Carbon in the Arctic.
260 1 $a Ann Arbor : $b ProQuest Dissertations & Theses, $c 2016
300 $a 164 p.
500 $a Source: Dissertation Abstracts International, Volume: 78-06(E), Section: B.
500 $a Adviser: Qinbin Li.
502 $a Thesis (Ph.D.)--University of California, Los Angeles, 2016.
520 $a The Arctic is warming at twice the global rate over recent decades. To slow down this warming trend, there is growing interest in reducing the impact from short-lived climate forcers, such as black carbon (BC), because the benefits of mitigation are seen more quickly relative to CO2 reduction. To propose efficient mitigation policies, it is imperative to improve our understanding of BC distribution in the Arctic and to identify the sources. In this dissertation, we investigate the sensitivity of BC in the Arctic, including BC concentrations in snow (BCsnow) and BC concentrations in air (BCair), to emissions, dry deposition and wet scavenging using a global 3-D chemical transport model (CTM) GEOS-Chem. By including flaring emissions, estimating dry deposition velocity using resistance-in-series method, and including Wegener-Bergeron-Findeisen (WBF) in wet scavenging, simulated BCsnow in the eight Arctic sub-regions agree with the observations within a factor of two, and simulated BCair fall within the uncertainty range of observations. Specifically, we find that natural gas flaring emissions in Western Extreme North of Russia (WENR) strongly enhance BCsnow (by up to ?50%) and BCair (by 20--32%) during snow season in the so-called 'Arctic front', but has negligible impact on BC in the free troposphere. The updated dry deposition velocity over snow and ice is much larger than those used in most of global CTMs and agrees better with observation. The resulting BCsnow changes marginally because of the offsetting of higher dry and lower wet deposition fluxes. In contrast, surface BCair decreases strongly due to the faster dry deposition (by 27--68%). WBF occurs when the environmental vapor pressure is in between the saturation vapor pressure of ice crystals and water drops in mixed-phase clouds. As a result, water drops evaporate and releases BC particles in them back into the interstitial air. In most CTMs, WBF is either missing or represented by a uniform and low BC scavenging efficiency. In this dissertation, we relate WBF with temperature and ice mass fraction based on long-term observations in mixed-phase clouds. We find that WBF reduces BC scavenging efficiency globally, with larger decrease at higher latitude and altitude (from 8% in the tropics to 76% in the Arctic). WBF slows down and reduces wet deposition of BC and leave more BC in the atmosphere. Higher BC air results in larger dry deposition. The resulting total deposition is lower in mid-latitudes (by 12--34%) and higher in the Arctic (2--29%). Globally, including WBF significantly reduces the discrepancy of BCsnow (by ~50%), BCair (by ~50%), and washout ratios (by a factor of two to four). The remaining discrepancies in these variables suggest that in-cloud removal is likely still excessive over land. In the last part, we identify sources of surface atmospheric BC in the Arctic in springtime, when radiative forcing is the largest due to the high insolation and surface albedo. We find a large contribution from Asian anthropogenic sources (40--43%) and open biomass burning emissions from forest fires in South Siberia (29--41%). Outside the Arctic front, BC is strongly enhanced by episodic, direct transport events from Asia and Siberia after ~12 days of transport. In contrast, in the Arctic front, a large fraction of the Asian contribution is in the form of 'chronic' pollution on 1--2 month timescale. As such, it is likely that previous studies using 5- or 10-day trajectory analyses strongly underestimated the contribution from Asia to surface BC in the Arctic. Our results point toward an urgent need for better characterization of flaring emissions of BC (e.g. the emission factors, temporal and spatial distribution), extensive measurements of both the dry deposition of BC over snow and ice, and the scavenging efficiency of BC in mixed-phase clouds, particularly over Ocean. More measurements of 14C are needed to better understand sources of BC (fossil fuel combustion versus biomass burning) and to provide additional constrain on BC simulations.
590 $a School code: 0031.
650 4 $a Atmospheric sciences. $3 3168354
650 4 $a Atmospheric chemistry. $3 544140
650 4 $a Climate change. $2 bicssc $3 2079509
690 $a 0725
690 $a 0371
690 $a 0404
710 2 $a University of California, Los Angeles. $b Atmospheric and Oceanic Sciences. $3 3280663
773 0 $t Dissertation Abstracts International $g 78-06B(E).
790 $a 0031
791 $a Ph.D.
792 $a 2016
793 $a English
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=10246870